Regulatory requirement to mark firearms with second, hidden serial number

(a) In general Within 12 months after the date of the enactment of this Act, the Attorney General shall promulgate final regulations that require each firearm manufactured in the United States on or after the effective date of the regulation, to be marked with a serial number that is located inside the receiver of the firearm or that is visible only in infrared light, in addition to the serial number with which the firearm is otherwise required by law to be marked. (b) Definition of receiver Section 921(a) of title 18, United States Code, is amended— (1) in paragraph (3)— (A) by inserting, including an unfinished frame or receiver after such weapon; and (B) by striking or (D) any destructive device and inserting; (D) any destructive device; or (E) any combination of parts designed or intended for use in converting any device into a firearm and from which a firearm may be readily assembled; (2) in paragraph (10)— (A) by striking and the and inserting the; and (B) by inserting; and the term manufacturing firearms shall include assembling a functional firearm from an unfinished frame or receiver or from molding, machining, or 3D printing a frame or receiver, and shall not include making or fitting special barrels, stocks, or trigger mechanisms to firearms before the period; and (3) by inserting after paragraph (30) the following: (31) The term unfinished frame or receiver means any forging, casting, printing, extrusion, machined body or similar article that— (A) has reached a stage in manufacture at which it may readily be completed, assembled, or converted to be used as the frame or receiver of a functional firearm; or (B) is marketed or sold to the public to become or be used as the frame or receiver of a functional firearm once completed, assembled, or converted..